Preheat the oven to 200C (fan oven 180C), gas mark 6. Line an edged baking sheet with greaseproof paper.
Cook the onion slowly in the butter in a frying pan until very soft and golden - this should take a good 15 minutes. Stir in the conserve, capers and tomato purée. Leave to cool.
Make a slit along one side of each pepper and open out a little, remove any seeds and discard. Divide the onion mixture between the peppers. Beat about half the egg into the goats' cheese in a small bowl and then spoon this over the onion mixture.
Brush the peppers all over with the remaining egg and then pat with the breadcrumbs. Place the peppers on the prepared baking sheet.
Bake the peppers in the preheated oven for 20-25 minutes or until just tender and golden brown.
Look for large packs of Japanese Panko breadcrumbs in Asian supermarkets. They are a variety of flaky breadcrumb used in cooking as a crunchy coating for fried foods. Panko is made from bread without crusts, and it has a crispier, airier texture than most other dried crumbs.